The present invention relates generally to control systems for internal combustion engines, and more particularly, to a compensating voltage controller system.
Many previously known motor vehicle throttle controls have a direct physical linkage between an accelerator pedal and the throttle body so that the throttle plate is pulled open by the accelerator cable as the driver presses the pedal. The direct mechanical linkage includes biasing that defaults the linkage to a reduced operating position, thus limiting engine output. Nevertheless, such mechanisms are often simple and unable to offer optimal fuel conservation, emissions efficiency, and performance to changing traveling conditions.
An alternative control for improving throttle control and this carefully controlled introduction of fuel air mixture into the engine cylinders is afforded by electronic throttle control.
The electronic throttle control includes a throttle control unit that positions the throttle plate by an actuator controlled by a microprocessor based on the present operating state determined by sensors. A microcontroller is typically included as part of a powertrain electronic control that can adjust the fuel air intake and ignition in response to changing conditions of vehicle operation as well as operator control.
Typical electronic throttle controls control the position of the actuator using either a variable current source or a variable voltage source. Unfortunately, both of these approaches have drawbacks. A current source driving a motor has a less xe2x80x9cnaturalxe2x80x9d viscous damping than a voltage source driving a motor. Additionally, converting a voltage source (the vehicle battery) to a current source requires a fast feedback loop on current, which is difficult to implement using H-driver technology.
A voltage source driving an electric motor has different disadvantages. Because motor temperature affects motor resistance, the voltage to torque transfer function changes. This unintended gain change results in a control system where gains have to be reduced to accommodate the motor resistance variability. Other considerations, such as, stability, overshoot, and position, limit any possible gain reduction. One possible remedy would be to modify the controller using feedback from temperature sensor. Unfortunately, this adds additional cost and complexity to the system.
The disadvantages associated with these conventional electronic throttle control techniques have made it apparent that a new technique for electronic throttle control is needed. The new technique should provide xe2x80x9cnaturalxe2x80x9d viscous damping (associated with voltage control) while compensating for motor temperature changes (associated with current control). Additionally, the new technique should negligibly increase overall system cost and complexity. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable compensating voltage controller system. Another object of the invention is to provide xe2x80x9cnaturalxe2x80x9d viscous motor damping while compensating for motor temperature changes. An additional object of the invention is to maintain current overall system cost and complexity.
In accordance with the objects of this invention, a compensating voltage controller system is provided. In one embodiment of the invention, an electronic throttle control apparatus includes a variable voltage source, such as an H-driver modulating battery voltage, controlling the position of a throttle motor by generating a variable voltage signal. A current sensing element is coupled to the H-driver and generates a voltage proportional to the current passing through both the H-driver and motor. A microprocessor is coupled to the H-driver and the current sensing element. The microprocessor determines electronic motor resistance based upon the voltage applied by the H-driver and the current sensing voltage signal. The microprocessor may then modify applied motor voltage based upon the calculated electronic throttle motor resistance.
The present invention thus achieves an improved compensating voltage controller system. The present invention is advantageous in that it allows the use of an H-driver voltage source while achieving the advantages of a current source.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.